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From: Peter Zijlstra <peterz@infradead.org>
To: Andy Lutomirski <luto@kernel.org>
Cc: x86@kernel.org, Dave Hansen <dave.hansen@intel.com>,
	LKML <linux-kernel@vger.kernel.org>,
	linux-mm@kvack.org, Andrew Morton <akpm@linux-foundation.org>,
	Mathieu Desnoyers <mathieu.desnoyers@efficios.com>,
	Nicholas Piggin <npiggin@gmail.com>,
	Russell King <linux@armlinux.org.uk>,
	linux-arm-kernel@lists.infradead.org,
	Will Deacon <will@kernel.org>
Subject: Re: [PATCH 7/8] membarrier: Remove arm (32) support for SYNC_CORE
Date: Wed, 16 Jun 2021 12:20:06 +0200	[thread overview]
Message-ID: <YMnQVoKvM5G34Yan@hirez.programming.kicks-ass.net> (raw)
In-Reply-To: <YMnPezLs6vb418Wz@hirez.programming.kicks-ass.net>

On Wed, Jun 16, 2021 at 12:16:27PM +0200, Peter Zijlstra wrote:
> On Tue, Jun 15, 2021 at 08:21:12PM -0700, Andy Lutomirski wrote:
> > On arm32, the only way to safely flush icache from usermode is to call
> > cacheflush(2).  This also handles any required pipeline flushes, so
> > membarrier's SYNC_CORE feature is useless on arm.  Remove it.
> 
> So SYNC_CORE is there to help an architecture that needs to do something
> per CPU. If I$ invalidation is broadcast and I$ invalidation also
> triggers the flush of any uarch caches derived from it (if there are
> any).

Incomplete sentence there: + then we don't need SYNC_CORE.

> Now arm_syscall() NR(cacheflush) seems to do flush_icache_user_range(),
> which, if I read things right, end up in arch/arm/mm/*.S, but that
> doesn't consider cache_ops_need_broadcast().
> 
> Will suggests that perhaps ARM 11MPCore might need this due to their I$
> flush maybe not being broadcast


  reply	other threads:[~2021-06-16 10:21 UTC|newest]

Thread overview: 91+ messages / expand[flat|nested]  mbox.gz  Atom feed  top
2021-06-16  3:21 [PATCH 0/8] membarrier cleanups Andy Lutomirski
2021-06-16  3:21 ` [PATCH 1/8] membarrier: Document why membarrier() works Andy Lutomirski
2021-06-16  4:00   ` Nicholas Piggin
2021-06-16  7:30     ` Peter Zijlstra
2021-06-17 23:45       ` Andy Lutomirski
2021-06-16  3:21 ` [PATCH 2/8] x86/mm: Handle unlazying membarrier core sync in the arch code Andy Lutomirski
2021-06-16  4:25   ` Nicholas Piggin
2021-06-16 18:31     ` Andy Lutomirski
2021-06-16 17:49   ` Mathieu Desnoyers
2021-06-16 18:31     ` Andy Lutomirski
2021-06-16  3:21 ` [PATCH 3/8] membarrier: Remove membarrier_arch_switch_mm() prototype in core code Andy Lutomirski
2021-06-16  4:26   ` Nicholas Piggin
2021-06-16 17:52   ` Mathieu Desnoyers
2021-06-16  3:21 ` [PATCH 4/8] membarrier: Make the post-switch-mm barrier explicit Andy Lutomirski
2021-06-16  4:19   ` Nicholas Piggin
2021-06-16  7:35     ` Peter Zijlstra
2021-06-16 18:41       ` Andy Lutomirski
2021-06-17  1:37         ` Nicholas Piggin
2021-06-17  2:57           ` Andy Lutomirski
2021-06-17  5:32             ` Andy Lutomirski
2021-06-17  6:51               ` Nicholas Piggin
2021-06-17 23:49                 ` Andy Lutomirski
2021-06-19  2:53                   ` Nicholas Piggin
2021-06-19  3:20                     ` Andy Lutomirski
2021-06-19  4:27                       ` Nicholas Piggin
2021-06-17  9:08               ` [RFC][PATCH] sched: Use lightweight hazard pointers to grab lazy mms Peter Zijlstra
2021-06-17  9:10                 ` Peter Zijlstra
2021-06-17 10:00                   ` Nicholas Piggin
2021-06-17  9:13                 ` Peter Zijlstra
2021-06-17 14:06                   ` Andy Lutomirski
2021-06-17  9:28                 ` Peter Zijlstra
2021-06-17 14:03                   ` Andy Lutomirski
2021-06-17 14:10                 ` Andy Lutomirski
2021-06-17 15:45                   ` Peter Zijlstra
2021-06-18  3:29                 ` Paul E. McKenney
2021-06-18  5:04                   ` Andy Lutomirski
2021-06-17 15:02               ` [PATCH 4/8] membarrier: Make the post-switch-mm barrier explicit Paul E. McKenney
2021-06-18  0:06                 ` Andy Lutomirski
2021-06-18  3:35                   ` Paul E. McKenney
2021-06-17  8:45         ` Peter Zijlstra
2021-06-16  3:21 ` [PATCH 5/8] membarrier, kthread: Use _ONCE accessors for task->mm Andy Lutomirski
2021-06-16  4:28   ` Nicholas Piggin
2021-06-16 18:08   ` Mathieu Desnoyers
2021-06-16 18:45     ` Andy Lutomirski
2021-06-16  3:21 ` [PATCH 6/8] powerpc/membarrier: Remove special barrier on mm switch Andy Lutomirski
2021-06-16  4:36   ` Nicholas Piggin
2021-06-16  3:21 ` [PATCH 7/8] membarrier: Remove arm (32) support for SYNC_CORE Andy Lutomirski
2021-06-16  9:28   ` Russell King (Oracle)
2021-06-16 10:16   ` Peter Zijlstra
2021-06-16 10:20     ` Peter Zijlstra [this message]
2021-06-16 10:34       ` Russell King (Oracle)
2021-06-16 11:10         ` Peter Zijlstra
2021-06-16 13:22           ` Russell King (Oracle)
2021-06-16 15:04             ` Catalin Marinas
2021-06-16 15:23               ` Russell King (Oracle)
2021-06-16 15:45                 ` Catalin Marinas
2021-06-16 16:00                   ` Catalin Marinas
2021-06-16 16:27                     ` Russell King (Oracle)
2021-06-17  8:55                       ` Krzysztof Hałasa
2021-06-18 12:54                       ` Linus Walleij
2021-06-18 13:19                         ` Russell King (Oracle)
2021-06-18 13:36                         ` Arnd Bergmann
2021-06-17 10:40   ` Mark Rutland
2021-06-17 11:23     ` Russell King (Oracle)
2021-06-17 11:33       ` Mark Rutland
2021-06-17 13:41         ` Andy Lutomirski
2021-06-17 13:51           ` Mark Rutland
2021-06-17 14:00             ` Andy Lutomirski
2021-06-17 14:20               ` Mark Rutland
2021-06-17 15:01               ` Peter Zijlstra
2021-06-17 15:13                 ` Peter Zijlstra
2021-06-17 14:16             ` Mathieu Desnoyers
2021-06-17 14:05           ` Peter Zijlstra
2021-06-18  0:07   ` Andy Lutomirski
2021-06-16  3:21 ` [PATCH 8/8] membarrier: Rewrite sync_core_before_usermode() and improve documentation Andy Lutomirski
2021-06-16  4:45   ` Nicholas Piggin
2021-06-16 18:52     ` Andy Lutomirski
2021-06-16 23:48       ` Andy Lutomirski
2021-06-18 15:27       ` Christophe Leroy
2021-06-16 10:20   ` Will Deacon
2021-06-16 23:58     ` Andy Lutomirski
2021-06-17 14:47   ` Mathieu Desnoyers
2021-06-18  0:12     ` Andy Lutomirski
2021-06-18 16:31       ` Mathieu Desnoyers
2021-06-18 19:58         ` Andy Lutomirski
2021-06-18 20:09           ` Mathieu Desnoyers
2021-06-19  6:02             ` Nicholas Piggin
2021-06-19 15:50               ` Andy Lutomirski
2021-06-20  2:10                 ` Nicholas Piggin
2021-06-17 15:16   ` Mathieu Desnoyers
2021-06-18  0:13     ` Andy Lutomirski

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